chore: convert @packages/icons to a compiled package and convert tests to vitest

[AtofStryker]

• Closes

Additional details

Converts @packages/icons to use vitest and removes the ts-node entrypoint making ESM possible. The tests before weren't actually being run in CI. This adds the icons package to the test script so the tests are now executed

Steps to test

How has the user experience changed?

PR Tasks

• Have tests been added/updated?
• Has a PR for user-facing changes been opened in cypress-documentation?
• Have API changes been updated in the type definitions?

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Note

Compiles @packages/icons with CJS/ESM entrypoints, migrates tests to Vitest, and adds the package to the root test run while updating related configs/docs.

• @packages/icons:
  • Build/Outputs: Add dual builds with index.js (CJS) and index.mjs (ESM); introduce tsconfig.cjs.json/tsconfig.esm.json and shared tsconfig.base.json; update package.json scripts (build, build-assets, build:cjs, build:esm) and fields (module, types); use tsx for build scripts; adjust dist path in index.ts.
  • Testing: Replace Mocha/Chai with Vitest (vitest.config.ts, new test/icons.spec.ts), remove old test/icons_spec.ts; switch test-unit to vitest run; add ignore rules for built artifacts.
• Repo/Docs:
  • Root tests: Include @packages/icons in top-level test script.
  • Guide: Update guides/esm-migration.md to mark packages/icons as completed and tidy https-proxy entries.

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[cypress]

cypress    Run #66213

Run Properties:   Passed #66213  •  3cf811e60c: correctly configure ES Module for packages/icons

Project	cypress
Branch Review	chore/icons_vitest
Run status	Passed #66213
Run duration	10m 53s
Commit	3cf811e60c: correctly configure ES Module for packages/icons
Committer	Bill Glesias
View all properties for this run ↗︎

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Test results
Failures	0
Flaky	0
Pending	3
Skipped	0
Passing	857
View all changes introduced in this branch ↗︎

UI Coverage  45.7%
Untested elements	137
Tested elements	117

Accessibility  97.36%
Failed rules	3 critical   7 serious   2 moderate   1 minor
Failed elements	77